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Deploying to main from @ 2xiao/leetcode-js@5995cd3 🚀
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‎plan/contest_list.md

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| 题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
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| :------: | :------ | :------: | :------ | :------: | :------: |
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| 3242 | 设计相邻元素求和服务 | | [`设计`](/tag/design.md) [`数组`](/tag/array.md) [`哈希表`](/tag/hash-table.md) `2+` | 🟢 | [🀄️](https://leetcode.cn/problems/design-neighbor-sum-service) [🔗](https://leetcode.com/problems/design-neighbor-sum-service) |
207-
| 3243 | 新增道路查询后的最短距离 I | | [`广度优先搜索`](/tag/breadth-first-search.md) [`图`](/tag/graph.md) [`数组`](/tag/array.md) | 🟠 | [🀄️](https://leetcode.cn/problems/shortest-distance-after-road-addition-queries-i) [🔗](https://leetcode.com/problems/shortest-distance-after-road-addition-queries-i) |
207+
| 3243 | 新增道路查询后的最短距离 I | [[✓]](/problem/3243.md) | [`广度优先搜索`](/tag/breadth-first-search.md) [`图`](/tag/graph.md) [`数组`](/tag/array.md) | 🟠 | [🀄️](https://leetcode.cn/problems/shortest-distance-after-road-addition-queries-i) [🔗](https://leetcode.com/problems/shortest-distance-after-road-addition-queries-i) |
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| 3244 | 新增道路查询后的最短距离 II | | [`贪心`](/tag/greedy.md) [`图`](/tag/graph.md) [`数组`](/tag/array.md) `1+` | 🔴 | [🀄️](https://leetcode.cn/problems/shortest-distance-after-road-addition-queries-ii) [🔗](https://leetcode.com/problems/shortest-distance-after-road-addition-queries-ii) |
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| 3245 | 交替组 III | | [`树状数组`](/tag/binary-indexed-tree.md) [`数组`](/tag/array.md) | 🔴 | [🀄️](https://leetcode.cn/problems/alternating-groups-iii) [🔗](https://leetcode.com/problems/alternating-groups-iii) |
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@@ -912,7 +912,7 @@ headerDepth: 0
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| 题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
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| :------: | :------ | :------: | :------ | :------: | :------: |
914914
| 2923 | 找到冠军 I | | [`数组`](/tag/array.md) [`矩阵`](/tag/matrix.md) | 🟢 | [🀄️](https://leetcode.cn/problems/find-champion-i) [🔗](https://leetcode.com/problems/find-champion-i) |
915-
| 2924 | 找到冠军 II | | [`图`](/tag/graph.md) | 🟠 | [🀄️](https://leetcode.cn/problems/find-champion-ii) [🔗](https://leetcode.com/problems/find-champion-ii) |
915+
| 2924 | 找到冠军 II | [[✓]](/problem/2924.md) | [`图`](/tag/graph.md) | 🟠 | [🀄️](https://leetcode.cn/problems/find-champion-ii) [🔗](https://leetcode.com/problems/find-champion-ii) |
916916
| 2925 | 在树上执行操作以后得到的最大分数 | | [`树`](/tag/tree.md) [`深度优先搜索`](/tag/depth-first-search.md) [`动态规划`](/tag/dynamic-programming.md) | 🟠 | [🀄️](https://leetcode.cn/problems/maximum-score-after-applying-operations-on-a-tree) [🔗](https://leetcode.com/problems/maximum-score-after-applying-operations-on-a-tree) |
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| 2926 | 平衡子序列的最大和 | | [`树状数组`](/tag/binary-indexed-tree.md) [`线段树`](/tag/segment-tree.md) [`数组`](/tag/array.md) `2+` | 🔴 | [🀄️](https://leetcode.cn/problems/maximum-balanced-subsequence-sum) [🔗](https://leetcode.com/problems/maximum-balanced-subsequence-sum) |
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| 2574 | 左右元素和的差值 | | [`数组`](/tag/array.md) [`前缀和`](/tag/prefix-sum.md) | 🟢 | [🀄️](https://leetcode.cn/problems/left-and-right-sum-differences) [🔗](https://leetcode.com/problems/left-and-right-sum-differences) |
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| 2575 | 找出字符串的可整除数组 | | [`数组`](/tag/array.md) [`数学`](/tag/math.md) [`字符串`](/tag/string.md) | 🟠 | [🀄️](https://leetcode.cn/problems/find-the-divisibility-array-of-a-string) [🔗](https://leetcode.com/problems/find-the-divisibility-array-of-a-string) |
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| 2576 | 求出最多标记下标 | | [`贪心`](/tag/greedy.md) [`数组`](/tag/array.md) [`双指针`](/tag/two-pointers.md) `2+` | 🟠 | [🀄️](https://leetcode.cn/problems/find-the-maximum-number-of-marked-indices) [🔗](https://leetcode.com/problems/find-the-maximum-number-of-marked-indices) |
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| 2577 | 在网格图中访问一个格子的最少时间 | | [`广度优先搜索`](/tag/breadth-first-search.md) [`图`](/tag/graph.md) [`数组`](/tag/array.md) `3+` | 🔴 | [🀄️](https://leetcode.cn/problems/minimum-time-to-visit-a-cell-in-a-grid) [🔗](https://leetcode.com/problems/minimum-time-to-visit-a-cell-in-a-grid) |
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| 2577 | 在网格图中访问一个格子的最少时间 | [[✓]](/problem/2577.md) | [`广度优先搜索`](/tag/breadth-first-search.md) [`图`](/tag/graph.md) [`数组`](/tag/array.md) `3+` | 🔴 | [🀄️](https://leetcode.cn/problems/minimum-time-to-visit-a-cell-in-a-grid) [🔗](https://leetcode.com/problems/minimum-time-to-visit-a-cell-in-a-grid) |
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## Weekly Contest 333 (2023年02月19日 10:30)
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| 2287 | 重排字符形成目标字符串 | | [`哈希表`](/tag/hash-table.md) [`字符串`](/tag/string.md) [`计数`](/tag/counting.md) | 🟢 | [🀄️](https://leetcode.cn/problems/rearrange-characters-to-make-target-string) [🔗](https://leetcode.com/problems/rearrange-characters-to-make-target-string) |
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| 2288 | 价格减免 | | [`字符串`](/tag/string.md) | 🟠 | [🀄️](https://leetcode.cn/problems/apply-discount-to-prices) [🔗](https://leetcode.com/problems/apply-discount-to-prices) |
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| 2289 | 使数组按非递减顺序排列 | | [`栈`](/tag/stack.md) [`数组`](/tag/array.md) [`链表`](/tag/linked-list.md) `1+` | 🟠 | [🀄️](https://leetcode.cn/problems/steps-to-make-array-non-decreasing) [🔗](https://leetcode.com/problems/steps-to-make-array-non-decreasing) |
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| 2290 | 到达角落需要移除障碍物的最小数目 | | [`广度优先搜索`](/tag/breadth-first-search.md) [`图`](/tag/graph.md) [`数组`](/tag/array.md) `3+` | 🔴 | [🀄️](https://leetcode.cn/problems/minimum-obstacle-removal-to-reach-corner) [🔗](https://leetcode.com/problems/minimum-obstacle-removal-to-reach-corner) |
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| 2290 | 到达角落需要移除障碍物的最小数目 | [[✓]](/problem/2290.md) | [`广度优先搜索`](/tag/breadth-first-search.md) [`图`](/tag/graph.md) [`数组`](/tag/array.md) `3+` | 🔴 | [🀄️](https://leetcode.cn/problems/minimum-obstacle-removal-to-reach-corner) [🔗](https://leetcode.com/problems/minimum-obstacle-removal-to-reach-corner) |
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## Biweekly Contest 79 (2022年05月28日 22:30)
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| 题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
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| :------: | :------ | :------: | :------ | :------: | :------: |
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| 2108 | 找出数组中的第一个回文字符串 | | [`数组`](/tag/array.md) [`双指针`](/tag/two-pointers.md) [`字符串`](/tag/string.md) | 🟢 | [🀄️](https://leetcode.cn/problems/find-first-palindromic-string-in-the-array) [🔗](https://leetcode.com/problems/find-first-palindromic-string-in-the-array) |
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| 2109 | 向字符串添加空格 | | [`数组`](/tag/array.md) [`双指针`](/tag/two-pointers.md) [`字符串`](/tag/string.md) `1+` | 🟠 | [🀄️](https://leetcode.cn/problems/adding-spaces-to-a-string) [🔗](https://leetcode.com/problems/adding-spaces-to-a-string) |
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| 2109 | 向字符串添加空格 | [[✓]](/problem/2109.md) | [`数组`](/tag/array.md) [`双指针`](/tag/two-pointers.md) [`字符串`](/tag/string.md) `1+` | 🟠 | [🀄️](https://leetcode.cn/problems/adding-spaces-to-a-string) [🔗](https://leetcode.com/problems/adding-spaces-to-a-string) |
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| 2110 | 股票平滑下跌阶段的数目 | | [`数组`](/tag/array.md) [`数学`](/tag/math.md) [`动态规划`](/tag/dynamic-programming.md) | 🟠 | [🀄️](https://leetcode.cn/problems/number-of-smooth-descent-periods-of-a-stock) [🔗](https://leetcode.com/problems/number-of-smooth-descent-periods-of-a-stock) |
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| 2111 | 使数组 K 递增的最少操作次数 | | [`数组`](/tag/array.md) [`二分查找`](/tag/binary-search.md) | 🔴 | [🀄️](https://leetcode.cn/problems/minimum-operations-to-make-the-array-k-increasing) [🔗](https://leetcode.com/problems/minimum-operations-to-make-the-array-k-increasing) |
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| 2094 | 找出 3 位偶数 | | [`数组`](/tag/array.md) [`哈希表`](/tag/hash-table.md) [`枚举`](/tag/enumeration.md) `1+` | 🟢 | [🀄️](https://leetcode.cn/problems/finding-3-digit-even-numbers) [🔗](https://leetcode.com/problems/finding-3-digit-even-numbers) |
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| 2095 | 删除链表的中间节点 | [[✓]](/problem/2095.md) | [`链表`](/tag/linked-list.md) [`双指针`](/tag/two-pointers.md) | 🟠 | [🀄️](https://leetcode.cn/problems/delete-the-middle-node-of-a-linked-list) [🔗](https://leetcode.com/problems/delete-the-middle-node-of-a-linked-list) |
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| 2096 | 从二叉树一个节点到另一个节点每一步的方向 | | [`树`](/tag/tree.md) [`深度优先搜索`](/tag/depth-first-search.md) [`字符串`](/tag/string.md) `1+` | 🟠 | [🀄️](https://leetcode.cn/problems/step-by-step-directions-from-a-binary-tree-node-to-another) [🔗](https://leetcode.com/problems/step-by-step-directions-from-a-binary-tree-node-to-another) |
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| 2097 | 合法重新排列数对 | | [`深度优先搜索`](/tag/depth-first-search.md) [`图`](/tag/graph.md) [`欧拉回路`](/tag/eulerian-circuit.md) | 🔴 | [🀄️](https://leetcode.cn/problems/valid-arrangement-of-pairs) [🔗](https://leetcode.com/problems/valid-arrangement-of-pairs) |
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| 2097 | 合法重新排列数对 | [[✓]](/problem/2097.md) | [`深度优先搜索`](/tag/depth-first-search.md) [`图`](/tag/graph.md) [`欧拉回路`](/tag/eulerian-circuit.md) | 🔴 | [🀄️](https://leetcode.cn/problems/valid-arrangement-of-pairs) [🔗](https://leetcode.com/problems/valid-arrangement-of-pairs) |
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## Weekly Contest 269 (2021年11月28日 10:30)
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<!-- prettier-ignore -->
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| 题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
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| :------: | :------ | :------: | :------ | :------: | :------: |
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| 1455 | 检查单词是否为句中其他单词的前缀 | | [`双指针`](/tag/two-pointers.md) [`字符串`](/tag/string.md) [`字符串匹配`](/tag/string-matching.md) | 🟢 | [🀄️](https://leetcode.cn/problems/check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence) [🔗](https://leetcode.com/problems/check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence) |
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| 1455 | 检查单词是否为句中其他单词的前缀 | [[✓]](/problem/1455.md) | [`双指针`](/tag/two-pointers.md) [`字符串`](/tag/string.md) [`字符串匹配`](/tag/string-matching.md) | 🟢 | [🀄️](https://leetcode.cn/problems/check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence) [🔗](https://leetcode.com/problems/check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence) |
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| 1456 | 定长子串中元音的最大数目 | [[✓]](/problem/1456.md) | [`字符串`](/tag/string.md) [`滑动窗口`](/tag/sliding-window.md) | 🟠 | [🀄️](https://leetcode.cn/problems/maximum-number-of-vowels-in-a-substring-of-given-length) [🔗](https://leetcode.com/problems/maximum-number-of-vowels-in-a-substring-of-given-length) |
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| 1457 | 二叉树中的伪回文路径 | | [`位运算`](/tag/bit-manipulation.md) [`树`](/tag/tree.md) [`深度优先搜索`](/tag/depth-first-search.md) `2+` | 🟠 | [🀄️](https://leetcode.cn/problems/pseudo-palindromic-paths-in-a-binary-tree) [🔗](https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree) |
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| 1458 | 两个子序列的最大点积 | | [`数组`](/tag/array.md) [`动态规划`](/tag/dynamic-programming.md) | 🔴 | [🀄️](https://leetcode.cn/problems/max-dot-product-of-two-subsequences) [🔗](https://leetcode.com/problems/max-dot-product-of-two-subsequences) |
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<!-- prettier-ignore -->
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| 题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
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| :------: | :------ | :------: | :------ | :------: | :------: |
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| 1346 | 检查整数及其两倍数是否存在 | | [`数组`](/tag/array.md) [`哈希表`](/tag/hash-table.md) [`双指针`](/tag/two-pointers.md) `2+` | 🟢 | [🀄️](https://leetcode.cn/problems/check-if-n-and-its-double-exist) [🔗](https://leetcode.com/problems/check-if-n-and-its-double-exist) |
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| 1346 | 检查整数及其两倍数是否存在 | [[✓]](/problem/1346.md) | [`数组`](/tag/array.md) [`哈希表`](/tag/hash-table.md) [`双指针`](/tag/two-pointers.md) `2+` | 🟢 | [🀄️](https://leetcode.cn/problems/check-if-n-and-its-double-exist) [🔗](https://leetcode.com/problems/check-if-n-and-its-double-exist) |
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| 1347 | 制造字母异位词的最小步骤数 | | [`哈希表`](/tag/hash-table.md) [`字符串`](/tag/string.md) [`计数`](/tag/counting.md) | 🟠 | [🀄️](https://leetcode.cn/problems/minimum-number-of-steps-to-make-two-strings-anagram) [🔗](https://leetcode.com/problems/minimum-number-of-steps-to-make-two-strings-anagram) |
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| 1348 | 推文计数 | | [`设计`](/tag/design.md) [`哈希表`](/tag/hash-table.md) [`二分查找`](/tag/binary-search.md) `2+` | 🟠 | [🀄️](https://leetcode.cn/problems/tweet-counts-per-frequency) [🔗](https://leetcode.com/problems/tweet-counts-per-frequency) |
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| 1349 | 参加考试的最大学生数 | | [`位运算`](/tag/bit-manipulation.md) [`数组`](/tag/array.md) [`动态规划`](/tag/dynamic-programming.md) `2+` | 🔴 | [🀄️](https://leetcode.cn/problems/maximum-students-taking-exam) [🔗](https://leetcode.com/problems/maximum-students-taking-exam) |

‎problem/0460.md

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| 题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
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| :------: | :------ | :------: | :------ | :------: | :------: |
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| 146 | LRU 缓存 | [[✓]](/problem/0146.md) | [`设计`](/tag/design.md) [`哈希表`](/tag/hash-table.md) [`链表`](/tag/linked-list.md) `1+` | 🟠 | [🀄️](https://leetcode.cn/problems/lru-cache) [🔗](https://leetcode.com/problems/lru-cache) |
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| 588 | 设计内存文件系统 🔒 | | [`设计`](/tag/design.md) [`字典树`](/tag/trie.md) [`哈希表`](/tag/hash-table.md) `2+` | 🔴 | [🀄️](https://leetcode.cn/problems/design-in-memory-file-system) [🔗](https://leetcode.com/problems/design-in-memory-file-system) |
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| 588 | 设计内存文件系统 🔒 | | [`设计`](/tag/design.md) [`字典树`](/tag/trie.md) [`哈希表`](/tag/hash-table.md) `2+` | 🔴 | [🀄️](https://leetcode.cn/problems/design-in-memory-file-system) [🔗](https://leetcode.com/problems/design-in-memory-file-system) |

‎problem/1346.md

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---
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title: 1346. 检查整数及其两倍数是否存在
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description: LeetCode 1346. 检查整数及其两倍数是否存在题解,Check If N and Its Double Exist,包含解题思路、复杂度分析以及完整的 JavaScript 代码实现。
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keywords:
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- LeetCode
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- 1346. 检查整数及其两倍数是否存在
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- 检查整数及其两倍数是否存在
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- Check If N and Its Double Exist
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- 解题思路
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- 数组
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- 哈希表
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- 双指针
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- 二分查找
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- 排序
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---
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# 1346. 检查整数及其两倍数是否存在
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🟢 <font color=#15bd66>Easy</font>&emsp; 🔖&ensp; [`数组`](/tag/array.md) [`哈希表`](/tag/hash-table.md) [`双指针`](/tag/two-pointers.md) [`二分查找`](/tag/binary-search.md) [`排序`](/tag/sorting.md)&emsp; 🔗&ensp;[`力扣`](https://leetcode.cn/problems/check-if-n-and-its-double-exist) [`LeetCode`](https://leetcode.com/problems/check-if-n-and-its-double-exist)
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## 题目
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Given an array `arr` of integers, check if there exist two indices `i` and `j`
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such that :
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- `i != j`
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- `0 <= i, j < arr.length`
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- `arr[i] == 2 * arr[j]`
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**Example 1:**
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> Input: arr = [10,2,5,3]
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>
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> Output: true
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>
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> Explanation: For i = 0 and j = 2, arr[i] == 10 == 2 _ 5 == 2 _ arr[j]
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**Example 2:**
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> Input: arr = [3,1,7,11]
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>
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> Output: false
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>
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> Explanation: There is no i and j that satisfy the conditions.
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**Constraints:**
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- `2 <= arr.length <= 500`
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- `-10^3 <= arr[i] <= 10^3`
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## 题目大意
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给你一个整数数组 `arr`,请你检查是否存在两个整数 `N` 和 `M`,满足 `N` 是 `M` 的两倍(即,`N = 2 * M`)。
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更正式地,检查是否存在两个下标 `i` 和 `j` 满足:
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- `i != j`
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- `0 <= i, j < arr.length`
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- `arr[i] == 2 * arr[j]`
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**示例 1:**
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> **输入:** arr = [10,2,5,3]
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>
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> **输出:** true
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>
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> **解释:** N = 10 是 M = 5 的两倍,即 10 = 2 \* 5 。
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**示例 2:**
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> **输入:** arr = [7,1,14,11]
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>
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> **输出:** true
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>
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> **解释:** N = 14 是 M = 7 的两倍,即 14 = 2 \* 7 。
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**示例 3:**
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> **输入:** arr = [3,1,7,11]
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>
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> **输出:** false
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>
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> **解释:** 在该情况下不存在 N 和 M 满足 N = 2 \* M 。
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**提示:**
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- `2 <= arr.length <= 500`
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- `-10^3 <= arr[i] <= 10^3`
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## 解题思路
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这道题可以使用哈希集合 (Set) 解决。
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- 遍历数组中的每个数字 `num`。
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- 对于每个 `num`,检查以下两种情况:
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- 是否存在 `2 * num` 在集合中(即 `num` 的两倍已出现)。
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- 是否存在 `num / 2` 在集合中(即 `num` 是某个数的两倍)。
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- 如果满足上述任意条件,则返回 `true`。
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- 否则,将当前数字添加到集合中。
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#### 复杂度分析
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- **时间复杂度**:`O(n)`,其中 `n` 是数组长度,需要遍历数组中的每个元素一次,每次查找和插入集合的复杂度为 `O(1)`,总时间复杂度为 `O(n)`,
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- **空间复杂度**:`O(n)`,使用一个集合来存储最多 `n` 个元素。
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## 代码
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```javascript
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/**
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* @param {number[]} arr
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* @return {boolean}
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*/
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var checkIfExist = function (arr) {
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let set = new Set();
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for (let num of arr) {
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// 检查 set 中是否存在 2 * num or num / 2
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if (set.has(2 * num) || set.has(num / 2)) {
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return true;
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}
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// 将当前数字加入 set 中
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set.add(num);
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}
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// 没找到两倍数
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return false;
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};
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```
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## 相关题目
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<!-- prettier-ignore -->
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| 题号 | 标题 | 题解 | 标签 | 难度 | 力扣 |
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| :------: | :------ | :------: | :------ | :------: | :------: |
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| 2154 | 将找到的值乘以 2 | | [`数组`](/tag/array.md) [`哈希表`](/tag/hash-table.md) [`排序`](/tag/sorting.md) `1+` | 🟢 | [🀄️](https://leetcode.cn/problems/keep-multiplying-found-values-by-two) [🔗](https://leetcode.com/problems/keep-multiplying-found-values-by-two) |

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